NGC 7789 Caroline's Rose from London

[markse68]

This is meant to be naked eye from a good sky but I have yet to see it through a scope- pretty sure I'm looking in the right area but not a hint of it with my 6" or 8" scopes at any mag from here in SE London. So I turned the AP scope to it and sure enough it really exists! 1 hr of subs in LRGB, KAF8300 CCD- really needs more subs to diminish the noise. 8" f4.5. Wish I could work out how to get less red more orangey stars and a bit less green and more blue. Processed in Siril with photometric calibration so 🤷‍♂️

Mark

[alacant]

59 minutes ago, markse68 said:

work out how to get less red

Hi

Nice image. Could be cc, filter, focus...

Post an unprocessed link to it if you like. That will help us.

[markse68]

Thanks Alacant. It would be interesting to see what you can do with it but will have to wait till tomorrow for the files.

It actually looks better on my phone lol.

I think it must be the CC- i’m using an MPCC iii currently but had same with previous RCC1- the red is always more bloated than the other filters. Could it be the city air? I thought dust etc was more transparent to red end of spectrum though (hence JWST) I focus in red to minimise this and don’t refocus, though i should.

The colours changed when i changed filters. I “upgraded” from Astronomik 2c to Astronomik Deep Sky. The 2c have a bit of overlap whilst the DS are discreet bands- maybe that’s causing it. With the 2c i remember there being more orange/yellow and bluer star colours where’s with the DS they tend towards red and green.

I always get a lot of green noise so use the removal tool in Siril but that turns it all a bit magenta 🤦‍♂️

The noisy 8300 really needs more subs than the 3x each filter here to smooth it out a bit. I don’t like using smoothing or noise reduction as I feel it leaves artefacts and looks artificial whenever i tried.

I’ll try it again next clear night we have doing 180sec exp rather than 300 and a lot more of them.

Mark

[Orange Smartie]

I was looking at this last night from a dark site in a 10" dob - it's visible, but it doesn't exactly leap out at you! Thanks for sharing 🙂

 

[markse68]

@alacant I have an interesting update. I submitted some data to the Hoys project but had some issues calibrating it so i sent a message to them warning them about it. Guess what- they replied to me questioning if by blue filter was really a blue filter as it didn’t look right! I’ll have to pull my filters and check but maybe i swapped the B and G in the wheel lol  and all this time i’ve been fighting the strange colour cast unnecessarily. Jeez 🤦‍♂️ Simple way to check of course- I’ll have a go at reprocessing it later today swapping the G and B 👍

Mark

Edited August 22, 2022 by markse68

[markse68]

Hi @alacant, here are the fits files.

I had another chat with Dirk from Hoys and he said that the green is definitely green (fits the green calibration data) but that the blue is more like green and should probably also be processed as green! So I don't think I was stupid and mixed them up.

I had another go at processing it this time using the Siril Linear Match tool to get the 3 colours average values the same and I think it gave more neutral colour balance and looks a bit better. Didn't need to do any green removal anyway so the background is more neutral.

Mark

 

 

r_pp_L_stacked_BKG.fit r_pp_R_stacked_BKG.fit r_pp_G_stacked_BKG.fit r_pp_B_stacked_BKG.fit

Edited August 22, 2022 by markse68

[alacant]

17 hours ago, markse68 said:

Dirk from Hoys

?

17 hours ago, markse68 said:

here are the fits files

All seems well apart from the colour. I think R may be out of focus. The only other glass the light traverses is the cc. Borrow one you know to be good to eliminate that?

But hey, for just 1 hour, this is good.

Cheers and HTH

 

 

[markse68]

48 minutes ago, alacant said:

?

All seems well apart from the colour. I think R may be out of focus. The only other glass the light traverses is the cc. Borrow one you know to be good to eliminate that?

But hey, for just 1 hour, this is good.

Cheers and HTH

 

Sorry yes Hoys is a citizen science project and I submitted some HaRGB data at the weekend and he (Dirk) queried if my blue filter was really blue as it didn't fit the calibration data very well. This fitted with what I'm seeing in terms of my stars being red/green rather than orange/blue that I would expect.

Yes about the red- I actually use the Bhatinov to focus with the red fllter in place as otherwise it's worse! It was always so even with the Astronomik 2C filters and the RCC1 coma corrector, and now the Astronomik Deep Sky filters and the MPCC iii coma corrector so I don't know what it is. I now have a GPU cc but haven't summoned the energy to try it and it will vignette more than the MPCC so not sure I want to use it anyway.

Thanks for having a look Alacant and your processing is an improvement!

Mark

[alacant]

8 hours ago, markse68 said:

GPU cc

We use the GPU. Anywhere between f5 and f3.9, we find it -far- superior than any of the affordable ccs. 

8 hours ago, markse68 said:

focus with the red fllter in place

Dunno. Try L and hope they're a little more par-focal?

Cheers

Edited August 23, 2022 by alacant